Place bread on a lightly floured surface. Roll dough to a 10 x 6-inch rectangle. Beginning 1/2 inch down from top of rectangle, and using a sharp knife, cut dough lengthwise into 3 equal strips, leaving strips attached at the top. Braid strips, pinching ends together to seal, and tucking ends under.
Place dough on a baking sheet lightly coated with cooking spray. Coat a piece of plastic wrap with cooking spray; place over braid. Let rise in a warm place (85°), free from drafts, 1 hour or until doubled in size. (Press two fingers into dough. If indentation remains, the dough has risen enough.)
Preheat oven to 350°.
Brush egg over dough. Sprinkle with sesame seeds. Bake at 350° for 25 minutes or until golden. Remove from baking sheet, and cool on a wire rack.